Published 7:53 am, Tuesday, April 22, 2014

DEAR DOCTOR K: My husband recently had a heart attack. Fortunately, he’s doing well. But I’d like to understand better what happens to the heart during a heart attack.

DEAR READER: The heart is a special kind of muscle that keeps blood circulating throughout your body. Your husband’s heart doesn’t just pump blood to the rest of his body; it also pumps blood to itself — it needs that blood to survive. Your husband’s heart attack occurred when a blood clot blocked a coronary artery — an artery that provides blood to his heart muscle. This prevented the artery from delivering oxygen-rich blood to a specific part of his heart’s muscular wall.

Usually, heart attacks cause pain and make the heart pump less efficiently. With minor heart attacks, heart function may not be impaired. With more serious heart attacks, heart failure or sudden death can follow.

Heart failure is a condition in which the heart is still pumping. However, it is pumping so weakly that blood is not circulating adequately. Not enough fresh, oxygen-rich blood is getting to the tissues of the body. Also, not enough blood is returning to the heart. This causes swelling, shortness of breath and other symptoms.

Sudden death is usually caused by a dangerous heart rhythm called ventricular fibrillation. Instead of working like a pump, the heart muscle just quivers. It doesn’t pump blood at all, leading to death. Fortunately, there are treatments that can restore a regular heart rhythm — and life.

During the early stages of a heart attack, heart cells are dying rapidly from a lack of oxygen. At this point, the primary goal is to unblock the artery and quickly restore blood flow to the injured heart muscle to limit permanent damage. This is called reperfusion therapy. The faster blood flow is restored to the heart, the greater the chances of surviving and recovering.

Reperfusion is often done mechanically. The doctor threads a catheter carrying a small deflated balloon through a large blood vessel and past the blockage. He or she inflates the balloon to crush the clot and plaque. Most balloon catheters also have a wire mesh, called a stent, over the balloon. After the balloon is inflated, the stent remains in place to keep the artery open.

Doctors also often give the patient various medications. These help prevent further blood clotting in the coronary arteries and minimize the heart’s oxygen needs. Bed rest immediately following a heart attack also helps reduce the heart’s oxygen needs.

With colleagues at Orca Health, I and my colleagues at Harvard have recently published inexpensive iBooks for the Apple iPad and iPhone on various heart conditions. One is about heart attack; another is about angioplasty and stent. A third is about heart failure, and a fourth is on sudden death.

These inexpensive iBooks explain each of these conditions, not just with words, but also with spectacular videos, animations and interactive tools. You can learn more about them on my website, Ask DoctorK.com.

Dr. Komaroff is a physician and professor at Harvard Medical School. AskDoctorK.com